A novel acid-catalyzed rearrangement of 9,10-diaryl-9,10-dihydroanthracene-9,10-diols affording 10,10 '-diaryl-9-anthrones.

Usually, 9,10-diarylanthracenes can be obtained by reduction of the corresp onding 9,10-diaryl-9,10-dihydroanthracene-9,10-diols with KI/NaH2PO2 in ace tic acid. In contrast, we found that in case of heteroaromatic aryl substit uents and when peri substituents are present on the anthracene residue, hig h amounts of anthrones are formed. These anthrones can be considered to res ult from a vinylogous pinacol rearrangement of the initial diol. To the bes t of our knowledge, this type of rearrangement is rarely observed, and me 1 0,10'-diaryl-9-anthrones obtained in this way, are difficult to prepare oth erwise. We prepared a number of such compounds and studied the mechanism of the transformation involved. The results are in agreement with a bridged t ransition state 10. (C) 1999 Elsevier Science Ltd. All rights reserved.